The overall objective of this research is to understand the role of mRNA in the regulated biosynthesis and cellular processing of parathyroid hormone (PTH). The specific objectives of this research are to: 1) study the structure and function of pre-ProPTH; 2) study the structure, transcription and translation of PTH mRNA; and 3) develop defined cell free systems in which the transcription and translation of PTH mRNA can be studied. We have isolated substantial quantities of bovine PTH mRNA which is about 50% pure and have prepared DNA complementary (cDNA) to the RNA. We plan to use the cDNA to determine the sequence of the PTH mRNA, to assay for PTH mRNA in parathyroid tissue stimulated by low extracellular calcium concentrations and to determine the number of copies of the PTH gene in the bovine genome. The primary translation product of PTH mRNA in the wheat germ or reticulocyte cell free systems is a precursor, pre-ProPTH, which in the parathyroid cell is rapidly converted to ProPTH. We have shown that addition of dog pancreatic rough endoplasmic reticulum to the cell free systems results in the conversion of pre-ProPTH to ProPTH. We plan to examine the mechanism of this conversion.